N's double came after an agreed hesitation.
NS do not play a forcing pass and N cannot make a penalty double in this situation so the N double means "I don't know whether we should take the penalty or play the contract so I leave it to you to decide ". His alternative bids are pass, 5♠, or a new suit.
After the hand was over there followed a long discussion about the 5♠ bid after the hesitation. EW thought that N could have been influenced by the hesitation but NS countered by saying that, although N gave some thought, he did make a system bid with a clear meaning - it's your decision partner.
The real point to this is that there would inevitably be a pause for thought before N makes his final bid and so whatever S does will be challenged if he makes the right decision.
This, I believe, is not what the rules are there for. Of course, there are always two possibilities i.e. a logical alternative that must be considered and some may choose. After all, partner has already said that he cannot decide!
I am very interested in the expert views - other than " change the system!"